Expansion valve device

ABSTRACT

An expansion valve device includes an electric driver having a stepping motor so as to control an opening degree of a refrigerant passage by displacing a valve member in accordance with a rotation angle of the stepping motor. A controller drives the stepping motor in a micro step when a flow rate of refrigerant flowing through the refrigerant passage is equal to or less than a predetermined value, and drives the stepping motor in a full step when the flow rate of the refrigerant is larger than the predetermined value.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2011-12077filed on Jan. 24, 2011, the disclosure of which is incorporated hereinby reference in its entirety.

FIELD OF THE DISCLOSURE

The present invention relates to an expansion valve device.

BACKGROUND OF THE DISCLOSURE

JP-B2-2898906 describes an electric flow rate control valve (electricexpansion valve) used for controlling a flow rate of refrigerant for arefrigerating cycle. The electric flow rate control valve has a valvemember that opens or closes a valve port of a fluid passage using astepping motor. The valve member has a large diameter part and a smalldiameter part. In a small flow rate region, the flow rate is controlledby controlling only the small diameter part. In a large flow rateregion, the flow rate is controlled by controlling the large diameterpart. Thus, accuracy for controlling the flow rate in the small flowrate region is raised.

However, the construction is complicated in such two-step valve memberhaving the large diameter part and the small diameter part.

SUMMARY OF THE DISCLOSURE

In view of the foregoing and other problems, it is an object of thepresent invention to provide an expansion valve device having a simplevalve member that can raise the accuracy for controlling the flow ratein the small flow rate region.

According to an example of the present invention, an expansion valvedevice arranged in a refrigerating cycle so as to decompress and expandrefrigerant circulating in the refrigerating cycle includes a housing, avalve member, an electric driver, and a controller. The housing definesa refrigerant passage through which the refrigerant circulates. Thevalve member is arranged in the housing so as to change an openingdegree of the refrigerant passage. The electric driver has a steppingmotor, and controls the opening degree of the refrigerant passage bydisplacing the valve member in accordance with a rotation angle of thestepping motor. The controller drives and controls the stepping motor.The controller drives the stepping motor in a micro step when theopening degree is changed within a first flow rate region where a flowrate of the refrigerant flowing through the refrigerant passage is equalto or less than a predetermined value. The controller drives thestepping motor in a full step when the opening degree is changed withina second flow rate region where the flow rate of the refrigerant flowingthrough the refrigerant passage is larger than the predetermined value.

Accordingly, the accuracy for controlling the flow rate in the smallflow rate region can be raised.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a schematic view illustrating an expansion valve deviceaccording to an embodiment;

FIG. 2 is a schematic view illustrating a vehicle air-conditioner havingthe expansion valve device;

FIG. 3 is a graph illustrating a pattern of current supplied to A-phasecoil and B-phase coil of a motor of the expansion valve device;

FIG. 4 is a graph illustrating a relationship between a rotor positionand a torque curve in the motor;

FIG. 5 is a partially enlarged view of FIG. 4;

FIG. 6 is a graph illustrating a relationship between an actual rotorstop position and an ordered rotor stop position in the motor;

FIG. 7A is a graph illustrating a relationship between a torque curveand a load of the motor when a battery of the vehicle air-conditionerhas a voltage of 12V, and

FIG. 7B is a graph illustrating a relationship between a torque curveand a load of the motor when the battery of the vehicle air-conditionerhas a voltage of 8V;

FIG. 8A is a graph illustrating a relationship between a torque curveand a load of the motor when a constant current is applied to the motor,and

FIG. 8B is a graph illustrating a relationship between a torque curveand a load of the motor when the constant current is changed from FIG.8A in accordance with the load; and

FIG. 9 is a graph of a comparison example illustrating a relationshipbetween a torque curve and a load of a motor in which a constant currentapplied to the motor is not changed irrespective of the load.

DETAILED DESCRIPTION

Embodiments of the present invention will be described hereafterreferring to drawings. In the embodiments, a part that corresponds to amatter described in a preceding embodiment may be assigned with the samereference numeral, and redundant explanation for the part may beomitted. When only a part of a configuration is described in anembodiment, another preceding embodiment may be applied to the otherparts of the configuration. The parts may be combined even if it is notexplicitly described that the parts can be combined. The embodiments maybe partially combined even if it is not explicitly described that theembodiments can be combined, provided there is no harm in thecombination.

An expansion valve device according to an embodiment is applied to avariable throttle valve 50 shown in FIG. 1. An air-conditioning controldevice 10 controls the valve 50. FIG. 2 illustrates an air-conditionerapparatus for a vehicle using the valve 50.

As shown in FIG. 2, the air-conditioner apparatus has an air-conditionerunit 1 that performs an air-conditioning for a passenger compartment ofthe vehicle. Actuators in the unit 1 are controlled by the controldevice 10 such as ECU. The unit 1 has a refrigerating cycle 3constructed by a duct 2, a centrifugal type blower, an evaporator 27 anda gas cooler 22. The duct 2 defines an air passage that introducesconditioned-air into the passenger compartment. The blower generates airflow in the duct 2 toward the passenger compartment. The evaporator 27cools air flowing through the duct 2. The gas cooler 22 reheats the airwhich passed through the evaporator 27.

The duct 2 is arranged at a front side of the passenger compartment. Aninside air inlet 11 and an outside air inlet 12 are defined upstream ofthe duct 2 in the air flowing direction. The inside air inlet 11 intakesair inside of the passenger compartment (hereinafter referred as insideair). The outside air inlet 12 intakes air outside of the passengercompartment (hereinafter referred as outside air). A switching door 4 isrotatably disposed at inner sides of the inlets 11, 12. The door 4 isdriven by an actuator 13 such as a servo motor, and changes the airinlet mode between an outside air introduction mode (FRS) and an insideair circulation mode (REC).

Plural air outlets (not shown) are defined downstream of the duct 2 inthe air flowing direction. The outlets includes at least a defrosteroutlet (DEF), a face outlet (FACE), and a foot outlet (FOOT). Thedefroster outlet blows off mainly warm air toward an inner surface of awindshield of the vehicle. The face outlet blows off mainly cold airtoward an occupant's upper body such as head or breast. The foot outletblows off mainly warm air toward an occupant's lower body such as foot.The air outlets are selectively opened or closed by plural mode-changingdoors (not shown). The mode-changing doors are driven by an actuator 14such as servo motor, thereby the air outlet mode (MODE) is switchedamong a face mode (FACE), a bilevel mode (B/L), afoot mode (FOOT), afoot defroster mode (F/D) and a defroster mode (DEF).

The centrifugal type blower has a centrifugal type fan 5 and a blowermotor 16 which rotates the fan 5. The fan 5 is rotatbly accommodated ina scroll casing that is integrally formed on the upstream side of theduct 2 in the air flowing direction. A rotation speed of the motor 16 ischanged based on a terminal voltage of the blower motor 16 appliedthrough a blower drive circuit (not shown), so that an amount of the airsent into the passenger compartment is controlled.

The refrigerating cycle 3 has a compressor 21, the gas cooler 22, afirst decompressor, an outdoor heat exchanger 24, an internal heatexchanger, a second decompressor, the evaporator 27, an accumulator 28,and a refrigerant pipe which connects them annularly.

The compressor 21 is rotated by an internal drive motor (not shown). Thecompressor 21 is an electric refrigerant compressor which compressesrefrigerant drawn from the evaporator 27 to have high temperature andhigh pressure equal to or higher than a critical pressure, for example,and discharges the refrigerant. The compressor 21 is turned on whenelectricity is supplied, and is stopped when the electricity supply isstopped. The rotating speed of the compressor 21 is controlled throughan inverter 20 so that the compressor 21 has a target rotating speedwhich is calculated by the ECU 10.

The gas cooler 22 is arranged in the duct 2, downstream of theevaporator 27 in the air flowing direction. The gas cooler 22 is a heatexchanger for heating the passing air through heat exchange with the gasrefrigerant which flows from the compressor 21.

Air mix (A/M) doors 6, 7 are rotatably supported by an air-inlet partand an air-outlet part of the gas cooler 22. The door 6, 7 controls atemperature of the air blown into the passenger compartment bycontrolling an amount of air passing through the gas cooler 22 and anamount of air bypassing the gas cooler 22. The door 6, 7 is driven by anactuator 15 such as servo motor.

The first decompressor is constructed by the variable throttle valve 50into which the gas refrigerant flows from the gas cooler 22. Thevariable throttle valve 50 is a first decompression device whichdecompresses the refrigerant which flows out of the gas cooler 22 basedon a valve opening, and may correspond to an electric expansion valvefor heating (EVH). The valve opening is electrically controlled by theECU 10. Moreover, the valve 50 can be set to have a full-open mode bythe ECU 10, so that the valve opening of the throttle valve 50 can befully opened.

The outdoor heat exchanger 24 is disposed at a place which is easy toreceive the running wind when the vehicle runs, outside of the duct 2,for example, a front part of an engine compartment of the vehicle. Heatexchange is performed between refrigerant which flows through the insideof the heat exchanger 24 and the outside air sent by an electric fan(not shown). The outdoor heat exchanger 24 operates as a heat sink whichabsorbs heat from outside air at a heating mode or dehumidificationmode, and operates as a radiator which radiates heat to outside air at acooling mode or dehumidification mode.

The internal heat exchanger is a refrigerant-refrigerant heat exchangerwhich superheats the refrigerant to be drawn into an inlet port of thecompressor 21. Heat exchange is performed between the high-temperaturerefrigerant flowing out of the outlet of the outdoor heat exchanger 24and the low-temperature refrigerant flowing out of the outlet of theaccumulator 28. The internal heat exchanger has two-layer heat exchangestructure in which a face of a low temperature side heat exchanger 29 istightly in contact with a face of a high temperature side heat exchanger25 so as to enable the heat exchange.

The second compressor has a variable throttle valve 26 and a bypass pipe33. Refrigerant flows into the throttle valve 26 from the hightemperature side heat exchanger 25 of the internal heat exchanger.Refrigerant flowing out of the high temperature side heat exchanger 25of the internal heat exchanger is sent to the accumulator 28 bybypassing the throttle valve 26 and the evaporator 27, due to the pipe33.

The variable throttle valve 26 is a second decompression device whichdecompresses the refrigerant which flows out of the high temperatureside heat exchanger 25 of the internal heat exchanger based on a valveopening. The variable throttle valve 26 is an electric expansion valvefor cooling (EVC), and the valve opening is electrically controlled bythe ECU 10. An electromagnetic open/close valve 34 (VH) is arranged inthe pipe 33. The valve 34 is opened when electricity is supplied, and isclosed when the electricity supply is stopped.

The evaporator 27 is an air-refrigerant heat exchanger (heat absorber).The refrigerant decompressed by the throttle valve 26 is evaporated byexchanging heat with air sent by the fan 5. Heat of the air is absorbedby the evaporator 27. The evaporator 27 supplies the gas refrigerant tothe low temperature side heat exchanger 29 of the internal heatexchanger and the compressor 21 through the accumulator 28. Theaccumulator 28 is a gas-liquid separating device which has a storagechamber for storing temporarily the refrigerant flowing from theevaporator 27.

A circulation circuit switching portion of the refrigerating cycle 3switches the operation mode of the refrigerating cycle 3, that is, thecirculation route of refrigerant in the refrigerating cycle 3 isswitched among a circulation circuit for the cooling mode (coolingcycle), a circulation circuit for the heating mode (heating cycle), anda circulation circuit for the dehumidification mode or thedehumidification heating mode (dehumidification cycle).

In the present embodiment, the variable throttle valve 50 and theelectromagnetic valve 34 may correspond to the circulation circuitswitching portion.

Specifically, when the variable throttle valve 50 for heating has thefull open mode, and when the electromagnetic valve 34 for heating isclosed, the operation mode of the refrigerating cycle 3 is set into thecooling cycle.

Moreover, when the valve 50 has a decompression mode in which therefrigerant is decompressed and expanded to have a small flow rate, andwhen the valve 34 is opened, the operation mode of the refrigeratingcycle 3 is set into the heating cycle.

Moreover, when the valve 50 has the decompression mode, and when thevalve 34 is closed, the operation mode of the refrigerating cycle 3 isset into the dehumidification cycle.

Here, the refrigerating cycle 3 of this embodiment uses a refrigerantwhose main component is made of carbon dioxide (CO₂) having low criticaltemperature. The refrigerating cycle 3 is a super critical vaporcompression type heat pump cycle. The refrigerant discharged from theoutlet port of the compressor 21 has a high pressure equal to or higherthan the critical pressure.

In the super critical vapor compression type heat pump cycle, therefrigerant temperature of the inlet part of the gas cooler 22 is raisedto about 120° C. by raising the refrigerant pressure on the highpressure side. The refrigerant temperature represents an inlettemperature of refrigerant. That is, the temperature of the refrigerantdischarged from the discharge port of the compressor 21 is raised toabout 120° C.

In addition, the refrigerant flowing into the gas cooler 22 is notcondensed even if the refrigerant radiates heat in the gas cooler 22,because the refrigerant is pressurized by the compressor 21 to have thepressure equal to or higher than the critical pressure.

The ECU 10 includes a known microcomputer having a central processingunit (CPU), a memory (ROM, RAM), an I/O port and a timer function, forexample. When an ignition switch of the vehicle is turned on (IG-ON),electricity is supplied to the ECU 10. The ECU 10 electrically controlseach actuator (the servo motor 13-15, the blower motor 16, the variablethrottle valve 26, 50, the electromagnetic valve 34, and the inverter20) of the air-conditioning unit 1 based on manipulate signal input froman air-conditioner console panel (not shown), sensor signal input fromvarious sensors, and a control program stored in the memory.

The air-conditioner console panel has a temperature setting switch, anair-conditioner (NC) switch, an air inlet setting switch (FRS/RECswitch), an air outlet setting switch (MODE switch), a defroster (DEF)switch, an air amount switch, an auto (AUTO) switch, a turn-off (OFF)switch and the like.

The air-conditioner (NC) switch is a cooling/dehumidification switchthat orders cooling/dehumidification for the passenger compartment. Theair-conditioner (NC) switch is a setting portion of thecooling/dehumidification that orders the cooling mode or thedehumidification mode among the operation modes of the refrigeratingcycle 3. The compressor 21 of the refrigerating cycle 3 may becompulsorily activated by turning on the NC switch, and may becompulsorily stopped by turning off the NC switch.

The DEF switch is a DEF mode fix switch which orders to fix the airoutlet mode into the DEF mode. The DEF switch is a fogging preventionswitch which removes or prevents the fogging of the windshield.

Further, the DEF switch is a dehumidification mode selecting portionwhich orders to fix the operation mode of the refrigerating cycle 3 intothe dehumidification mode. The dehumidification mode selecting portionsets the dehumidification mode which is one of a dehumidificationpriority mode or blow-off temperature priority mode.

Alternatively, the dehumidification mode selecting portion may be ananti-fogging sensor that detects the fogging of the windshield, otherthan the DEF switch. The dehumidification mode selecting portion may bea dehumidification switch that orders only the dehumidification in thepassenger compartment without fixing the air outlet mode into the DEFmode when the switch is turned on. The dehumidification mode selectingportion may be a anti-fogging switch that orders only the prevention ofthe fogging for the windshield without fixing the air outlet mode intothe DEF mode when the switch is turned on.

The AUTO switch is a switch which automatically sets the operation modeof the refrigerating cycle 3 into the cooling mode, the heating mode, orthe dehumidification mode based on at least a target blow offtemperature (TAO). The AUTO switch is an automatic control switch whichorders to automatically control each actuator of the air-conditioningunit 1. For example, when the MODE change switch or the air amountsetting switch is operated, automatic air-conditioning control forswitching the air outlet mode or for controlling the blower motor iscancelled.

A discharge pressure sensor 40 detects a discharge pressure (SP) of therefrigerant discharged from the outlet port of the compressor 21. Adischarge temperature sensor 41 detects a discharge temperature (TD) ofthe refrigerant discharged from the outlet port of the compressor 21. Afirst refrigerant temperature sensor 42 detects a refrigeranttemperature (TCO) discharged from the outlet part of the gas cooler 22.A second refrigerant temperature sensor 43 detects a refrigeranttemperature (THO) which flows out of the outlet part of the outdoor heatexchanger 24.

Sensor signals output from the sensors 40, 41, 42 and 43 have NDconversion at an input (ND conversion) circuit (not shown in FIG. 2,refer to an input processor 102 in FIG. 1), and the converted signal isinput into the microcomputer.

The discharge pressure sensor 40 is a high pressure detector thatdetects the high pressure of the refrigerating cycle 3. The dischargetemperature sensor 41 is also a refrigerant detector that detects theinlet temperature of the refrigerant which flows into the inlet part ofthe gas cooler 22.

An outside air temperature sensor 44 detects a temperature of outsideair (TAM) which is an air temperature outside of the passengercompartment. A temperature sensor 45 detects an air temperature (TE)just downstream of the evaporator 27, and may correspond to adehumidification capacity detector. An inside air temperature sensor 46detects a temperature of inside air (TR) which is an air temperatureinside of the passenger compartment. A solar sensor 47 detects a solarradiation amount (TS) into the passenger compartment. A temperaturesensor 48 detects an air temperature (TGC) just downstream of the gascooler 22, and may correspond to a heating capacity detector. Sensorsignals output from the sensors 44, 45, 46, 47 and 48 have A/Dconversion at the A/D conversion circuit, and the converted signal isinput into the microcomputer.

An operation of the air-conditioning apparatus will be describedhereinafter.

For example, when the ignition switch is active and when the electricityis supplied to the ECU 10, the ECU 10 selects the operation mode of therefrigerating cycle 3 based on the manipulate signal transmitted fromeach switch (not shown) of the air-conditioner console panel, the sensorsignal transmitted from the various sensors, and the control programstored in the memory. Thus, each actuator (the servo motor 13-15, theblower motor 16, the variable throttle valve 26, 50, the electromagneticvalve 34, and the inverter 20) of the air-conditioning unit 1 iselectrically controlled.

For example, when the AUTO switch is turned on so as to perform theautomatic air-conditioning control, the ECU 10 intakes the sensor signalfrom the various sensors, and the manipulate signal from theair-conditioner console panel. The signals are necessary for controllingeach air-conditioning member (actuator) in the air-conditioning unit 1.

Next, the target blow off temperature (TAO) of the conditioning airwhich is blown off into the passenger compartment is computed based on acomputing equation beforehand stored in the memory.

Next, the compressor operation judging is performed for determiningwhether the compressor 21 is turned on or off, based on theair-conditioner (A/C) switch, for example. When a result of thecompressor operation judging indicates the turning-on of the compressor21 based on the previously-computed target blow off temperature (TAO),an operation mode judging is performed for determining the operationmode of the refrigerating cycle 3.

In the operation mode judging, the target blow off temperature (TAO) iscompared with a first specified value α (for example, 45° C.) and asecond specified value β (for example, 15° C.). In the case of TAO≧α,the heating cycle (heating mode) is chosen as the operation mode of therefrigerating cycle 3. In the case of TAO≦β, the cooling cycle (coolingmode) is chosen as the operation mode of the refrigerating cycle 3. Inthe case of β<TAO<α, the dehumidification cycle (dehumidification mode)is chosen as the operation mode of the refrigerating cycle 3.

After the operation mode of the refrigerating cycle 3 is chosen, aterminal voltage impressed to the blower motor 16, an opening degree ofthe door 4 which changes the air inlet mode between the inside air modeand the outside air mode, an opening degree of the mode switching doorwhich change the air outlet mode, and an opening degree of the A/M door6, 7 are determined, and the actuators are controlled to drive theblower and the doors.

The operation mode of the refrigerating cycle 3 is set. Operationalstatus of the compressor 21 (rotating speed etc.), the opening degree ofthe variable throttle valve 50, 26, and the opening/closing state of theelectromagnetic valve 34 are set and controlled in a manner that thecycle efficiency of the refrigerating cycle 3 is maximized in eachoperation mode.

When the cooling mode is chosen as the operation mode of therefrigerating cycle 3, the variable throttle valve 50 has the full-openmode, and the electromagnetic valve 34 is closed. The refrigerantdischarged from the outlet of the compressor 21 circulates in order ofthe gas cooler 22, the full-opened valve 50, the outdoor heat exchanger24, the high temperature side heat exchanger 25, the valve 26, theevaporator 27, the accumulator 28, the low temperature side heatexchanger 29 and the compressor 21, as shown in a blank arrow directionof FIG. 2.

At this time, the opening degree of the A/M door 6, 7 is controlled tohave a full-close state (MAX-COOL). The refrigerant of high-temperatureand high-pressure discharged from the compressor 21 does not radiateheat while passing through the gas cooler 22. Therefore, the air cooledin the evaporator 27 flows through the duct 2 so as to bypass the gascooler 22. For example, the air is blown off from the FACE outlet intothe passenger compartment, so that the passenger compartment is cooledto have a preset temperature.

In the internal heat exchanger, heat is exchanged between the hightemperature and high pressure refrigerant flowing through the hightemperature side heat exchanger 25 from the outdoor heat exchanger 24and the low temperature and low pressure refrigerant flowing through thelow temperature side heat exchanger 29 from the accumulator 28. Thus,the high temperature and high pressure refrigerant flowing into theevaporator 27 is cooled. Thereby, the evaporator enthalpy increases, sothat the cycle efficiency of the refrigerating cycle 3 can be improvedby saving power or electricity.

When the heating mode is chosen as the operation mode of therefrigerating cycle 3, the variable throttle valve 50 has thedecompression mode, and the electromagnetic valve 34 is opened. Therefrigerant discharged from the outlet of the compressor 21 circulatesin order of the gas cooler 22, the valve 50, the outdoor heat exchanger24, the high temperature side heat exchanger 25, the valve 34, theaccumulator 28, the low temperature side heat exchanger 29 and thecompressor 21, as shown in a black arrow direction of FIG. 2. At thistime, the valve 26 may be fully closed.

At this time, the opening degree of the A/M door 6, 7 is controlled tohave a full-open state (MAX-HOT). The high temperature and high pressurerefrigerant discharged from the compressor 21 radiates heat to the airin the duct 2 while passing through the gas cooler 22. The air is blownoff from the FOOT outlet into the passenger compartment, so that thepassenger compartment is heated to have a preset temperature. In theinternal heat exchanger, heat exchange is not performed, because lowtemperature and low pressure refrigerant passes each of the heatexchangers 25, 29.

When the dehumidification mode is chosen as the operation mode of therefrigerating cycle 3, the variable throttle valve 50 has thedecompression mode, and the electromagnetic valve 34 is closed. Therefrigerant discharged from the outlet of the compressor 21 circulatesin order of the gas cooler 22, the valve 50, the outdoor heat exchanger24, the high temperature side heat exchanger 25, the valve 26, theevaporator 27, the accumulator 28, the low temperature side heatexchanger 29 and the compressor 21, as shown in a hatched arrowdirection of FIG. 2.

At this time, air is cooled and dehumidified in the evaporator 27, andthe air is reheated in the gas cooler 22. The air is blown off into thepassenger compartment from the DEF outlet or the FOOT outlet, forexample. The passenger compartment is dehumidified and heated in amanner that the passenger compartment has a preset temperature and in amanner that the fogging of the windshield is removed or prevented.

The discharge pressure of the refrigerant discharged from the compressor21 and the refrigerant pressure of the outdoor heat exchanger 24 arevariable by the throttling degree of the variable throttle valve 50, 26.Thus, the throttling degree is controlled in a manner that the heatingcapacity of the gas cooler 22 or the dehumidification capacity of theevaporator 27 has a target value. The heating capacity of the gas cooler22 may be represented by a temperature of air flowing out of the gascooler or flowing into the passenger compartment. The dehumidificationcapacity of the evaporator 27 may be represented by a temperature of airflowing out of the evaporator.

Specifically, if the throttling degree is controlled in a manner thatthe discharge pressure of the refrigerant discharged from the compressor21 and the refrigerant pressure of the outdoor heat exchanger 24 becomelow, the outdoor heat exchanger 24 operates as a heat sink, so that theheat amount radiated by the gas cooler 22 increases. At this time, forexample, the opening degree of the valve 50 is set as small and theopening degree of the valve 26 is set as large. Therefore, the blow offtemperature of the conditioned air blown into the passenger compartmenthas a comparatively high temperature.

In contrast, if the throttling degree is controlled in a manner that thedischarge pressure of the refrigerant discharged from the compressor 21and the refrigerant pressure of the outdoor heat exchanger 24 becomehigh, the outdoor heat exchanger 24 operates as a radiator, so that theheat amount radiated by the gas cooler 22 decreases. At this time, forexample, the opening degree of the valve 50 is set as large and theopening degree of the valve 26 is set as small. Therefore, the blow offtemperature of the conditioned air blown into the passenger compartmenthas a comparatively low temperature.

Next, the variable throttle valve 50 for heating and theair-conditioning control device 10 which controls the valve 50 will beexplained.

As shown in FIG. 1, the variable throttle valve 50 is constructed by ahousing 51, a seat component 52, a valve 53, a spring 54, a motor 55, aplate component 56, a ring component 57, and an O-ring 58.

The housing 51 is made of metal material, for example, and has anapproximately L-shaped refrigerant passage 51 a through which therefrigerant circulates. In the housing 51, the cylindrical seatcomponent 52 made of metal material is disposed at the bending part ofthe refrigerant passage 51 a so that inside space of the seat component52 defines a part of the refrigerant passage 51 a. The seat component 52has a top face, and an inner periphery of the top face defines a seat 52a.

The valve 53 is made of metal material, for example, and is disposed inthe refrigerant passage 51 a of the housing 51. A main part of the valve53 has an approximately truncated cone shape, and an outer periphery ofa lower end face of the valve 53 defines a seating part which is seatedto or separated from the seat 52 a of the seat component 52. The valve53 has a shaft 53 a extending upward from the main part in FIG. 2. Theshaft 53 a is arranged in a through hole part of the housing 51extending in the axis direction of the shaft 53 a, and an upper end ofthe shaft 53 a is located to project from the housing 51.

The motor 55 is constructed by a stepping motor, and is arranged on theupper side of the housing 51. The motor 55 has a case 553 having anapproximately dome shape constructed by a cylindrical part and ahemisphere part which closes the upper end of the cylindrical part. Aring-shaped stator 551 is arranged to the outer periphery side of thecylindrical part of the case 553, and a rotor 552 is arranged inside ofthe cylindrical part.

A lower end of the cylindrical part of the case 553 has a flange partextending outward in the radial direction. The O-ring 58 correspondingto a seal member is interposed between the flange part and the housing51. The metallic plate component 56 is screwed to the housing 51, andpresses the flange part onto the housing 51 through the ring component57 arranged above the flange part of the case 553. Thereby, the sealingcan be achieved between the housing 51 and the case 553 of the motor 55over all the circumference.

The stator 551 is arranged on the upper side of the plate component 56,and has two-phase structure constructed of an A phase coil 551A and a Bphase coil 551B. The motor 55 is, what is called, a two-phase steppingmotor.

The rotor 552 arranged in the case 553 is made of magnetic material. Therotor 552 has an approximately pillar-shaped main part 552 a and acylindrical magnet 552 b. A part of the main part 552 a is removed inring-recess shape from the both of the upper face and the lower face.The cylindrical magnet 552 b is made of a permanent magnet, and isarranged on the outer circumference face of the main part 552 a. Thecylindrical magnet 552 b is magnetized at even pitch in a rotationdirection of the rotor 552.

A concave portion is defined in the main part 552 a of the rotor 552,and is recessed upward from the center part of the lower face. The upperend of the shaft 53 a of the valve 53 is fixed to a ceiling face part ofthe concave portion.

A female thread is formed on the inner circumference face of the concaveportion of the main part 552 a of the rotor 552. On the other hand, acylindrical male thread part 51 b is fixed to the housing 51, andprojects upward. A male thread is formed on the outer circumference faceof the male thread part 51 b. The female thread of the main part 552 aof the rotor 552 and the male thread of the male thread part 51 b areengaged with each other. The rotor 552 is displaced in the axisdirection (up-and-down direction in FIG. 1) when the rotor 552 isrotated.

When the rotor 552 is rotated and is displaced in the axis direction,the valve 53 fixed to the main part 552 a of the rotor 552 is alsodisplaced, so as to change the opening degree between the valve 53 andthe seat 52 a.

A construction defined by the motor 55 and the male thread part 51 bthreaded to the rotor 552 may correspond to an electric driver having astepping motor and controlling an opening degree of a refrigerantpassage by displacing a valve member in accordance with a rotation angleof the stepping motor.

As clearly shown in FIG. 1, the shaft 53 a of the valve 53 has a steppart. The spring 54 is interposed between the step part and the ceilingface of the main part 552 a of the rotor 552. Thereby, if the rotor 552is displaced downward after the valve 53 is seated on the seat 52 a, thespring 54 is compressed, so that excess load is restricted from applyingto a seating part defined between the valve 53 and the seat 52 a.

Moreover, the rotor 552 is restricted from having excess rotationaldisplacement because a pin component 51 c projected from the housing 51and a pin component 552 c projected from the rotor 552 contact with eachother.

As shown in FIG. 1, the ECU 10 has an air-conditioning control 101, aninput processor 102 and a drive unit 103. The input processor 102processes a signal input from each switch or sensor, and the processedsignal is sent to the air-conditioning control 101. The drive unit 103outputs a value information determined by the control 101 as an electricsignal so as to control each actuator (the servo motor 13-15, the blowermotor 16, the throttle valve 26, the electromagnetic valve 34 or theinverter 20).

The ECU 10 further has a step drive control 111, a drive unit 113, andan input processor 112. The step drive control 111 receives a commandabout a valve opening of the valve 50 that is determined by theair-conditioning control 101, and determines a current value for themotor 50 based on the command. Specifically, a driving direction(rotation direction) of the motor 55 of the valve 50 and a number ofsteps in the driving of the motor 55 of the valve 50 are set by the stepdrive control 111, for example.

The drive unit 113 energizes the A-phase coil 551A and the B-phase coil551B of the stator 551 through PWM control based on the driveinformation of the valve 50 determined by the step drive control 111.The current values of the A phase coil 551A and the B phase coil 551Bare input into the input processor 112, and the input processor 112performs feedback control relative to the step drive control 111.

The step drive control 111, the input processor 112, and the drive unit113 may define a controller which drives and controls the steppingmotor.

When the cooling mode is selected as the operation mode of therefrigerating cycle 3, the air-conditioner control 101 outputs a valveopening command to the step drive control 111. The valve opening commandorders the variable throttle valve 50 to be fully opened.

When the heating mode or dehumidification mode (dehumidification heatingmode) is chosen as the operation mode of the refrigerating cycle 3, theair-conditioner control 101 outputs a valve opening command to the stepdrive control 111. The valve opening command orders the variablethrottle valve 50 to decompress and expand the refrigerant in a mannerthat the operation efficiency of the refrigerating cycle 3 becomesbetter for performing a desired air-conditioning.

When the step drive control 111 receives the valve opening command fromthe air-conditioner control 101, the step drive control 111 calculates adriving condition for controlling the position (valve opening) of thevalve 53 in the decompression mode where the variable throttle valve 50decompresses and expands the refrigerant. Further, the step drivecontrol 111 computes a driving condition for performing the mode changebetween the decompression mode and the full-open mode.

When the step drive control 111 controls the position of the valve 53 inthe decompression mode (that is, when the valve 53 is displaced in thelow flow rate region where the decompression and expansion isperformed), the step drive control 111 calculates a condition fordriving the motor 55 in a micro step. That is, the rotation direction(driving direction) of the rotor 552 and the number of micro steps arecalculated for displacing the valve 53 to an ordered valve openingposition. The number of micro steps represents the number of micro steppulses for the stepping motor 50.

When the step drive control 111 performs the mode change between themaximum flow rate time in the decompression mode and the full-open mode,the step drive control 111 calculates a condition for driving the motor55 in a full step. That is, the rotation direction of the rotor 552 andthe number of full steps (the number of full step pulses) are calculatedfor displacing the valve 53 to an ordered valve opening position:

A refrigerant flow rate region where the variable throttle valve 50decompresses and expands the refrigerant may correspond to a first flowrate region in this embodiment. A refrigerant flow rate region where theflow rate is larger than that in the first flow rate region maycorrespond to a second flow rate region in this embodiment. When thefull-open mode is selected, the valve 53 causes the opening degree ofthe refrigerant passage 51 a to have the maximum opening in a mannerthat the refrigerant flow rate has the maximum value in the second flowrate region.

When the motor 55 is driven in the full step, a gear tooth of the rotor552 such as magnetic pole of the cylindrical magnet 552 b is driven tomove by one step from a first position to a second position. The firstposition is a position opposing to a first gear tooth of the stator 551such as magnetic pole magnetized by each phase coil. The second positionis a position opposing to a second gear tooth of the stator 551 that isadjacent to the first gear tooth of the stator 551.

When the motor 55 is driven in the micro step, a gear tooth of the rotor552 is driven to move by plural steps from the first position to thesecond position. That is, in the micro step, a drive angle of the onestep in the full step drive is separated into the plural steps, and themotor 55 is stepwise driven by the plural steps. Therefore, it ispossible to stop the gear tooth of rotor 552 at a middle positionbetween the first position and the second position.

The step drive control 111 outputs a current command value to the driveunit 113 in a manner that the motor 55 is driven by a constant currentcorrespondingly to the calculated driving direction and the calculatednumber of pluses. The drive unit 113 supplies electricity to the A phasecoil 551A and the B phase coil 551B based on the current command value.

As shown in FIG. 1, a high pressure side refrigerant pressure sensor 40Ais arranged for detecting the pressure in the refrigerant passage 51 aupstream of the valve 53. The sensor 40A detects the pressure ofrefrigerant before decompressed by the throttle valve 50 in therefrigerating cycle. The sensor 40A is omitted in the explanation of therefrigerating cycle using FIG. 2.

The step drive control 111 changes the value of the constant currentdriving the motor 55 in accordance with the refrigerant pressuredetected by the sensor 40A. Specifically, the value of the constantcurrent is increased as the detected refrigerant pressure becomes high.

The sensor 40A is not limited to be placed in the refrigerant pipedirectly upstream of the throttle valve 50. For example, the sensor 40Amay be arranged in the housing 51 so as to face the refrigerant passage51 a upstream of the valve 53. A high pressure side pressure detectormay correspond to the sensor 40A, or a combination of the sensor 40A andthe discharge pressure sensor 40.

Although detailed explanation was omitted, the throttle valve 26 forcooling may have the same construction as the throttle valve 50 forheating. Therefore, the variable throttle valve 26 for cooling and thevariable throttle valve 50 for heating can be made common.

According to the embodiment, the step drive control 111 selectivelyswitches the decompression mode and the full-open mode, based on thevalve opening command output from the A/C control 101. The decompressionmode is selected when the throttle valve 50 is required to decompressthe refrigerant which circulates in the refrigerant passage 51 a, sothat the refrigerant is decompressed and expanded in the low flow rateregion. The full-open mode is selected when the throttle valve 50 is notrequired to decompress and expand the refrigerant which circulates inthe refrigerant passage 51 a, so that the valve 53 is positioned at themaximum opening position so as to have the maximum refrigerant flowrate.

In the decompression mode, the valve 53 is displaced by driving themotor 55 corresponding to the stepping motor in the micro step, and theflow rate control is performed for refrigerant.

When the mode change is performed between the decompression mode and thefull-open mode, the valve 53 is displaced by driving the motor 55 in thefull step.

Therefore, accuracy for controlling the refrigerant flow rate can beimproved at the decompression mode. Further, the mode change can bequickly performed between the decompression mode and the full-open mode.

Moreover, when the step drive control 111 drives the motor 55 throughthe drive unit 113, the step drive control 111 computes the drivingdirection and the number of pulses, and the motor 55 is driven by theconstant current in accordance with the drive pulse. Thereby, the motor55 constructed by the stepping motor can be driven stably.

When the mode change is performed between the decompression mode and thefull-open mode, the motor 55 is driven by the constant current,similarly to the decompression mode. At least, when the valve opening ischanged in the low flow rate region at the decompression mode, it isdesirable to drive the motor 55 in the micro step by using the constantcurrent. Thereby, even when a voltage supplied from a power source isvaried, the motor 55 can be stably driven in the micro step due to theconstant current.

Referring to FIGS. 3-7B, the reasons of the above advantages will bedescribed hereinafter. FIG. 3 shows a graph which illustrates a currentinput into the A phase coil and a current input into the B phase coilwhen the motor is driven in the micro step having sixteen separatedsteps. FIG. 4 shows a graph illustrating a torque curve that representsa relationship between the rotor angle (rotor position) and the torquewhen the current pattern of FIG. 3 is used. FIG. 5 shows an enlargedpart of the torque curve of FIG. 4.

As shown in FIG. 3, relative to an angle of the one step in the fullstep drive, the current supplied to the A phase coil is stepwiseincreased in the separated sixteen steps, and the current supplied tothe B phase coil is stepwise decreased in the separated sixteen steps. Aforce attracting the rotor 552 between the phases is gradually changedstep by step. It becomes possible to stop the rotor 552 at a point atwhich the attracting force is balanced each time, so that the micro stepdrive can be performed by dividing the angle in the full step drive intothe sixteen steps.

However, as shown in FIG. 4, the torque curve tends to have variation ina mountain portion or a valley portion at which an absolute value of thetorque is large. Further, a variation amount also becomes small in themountain portion and the valley portion because a gradient of the torquecurve becomes small.

Therefore, as shown in FIG. 5, a resolution of the rotor stop positionis lowered in a high-load case where the load of the motor 55 is highbecause the mountain portion or the valley portion is coincident withthe high-load case, compared with a low-load case. The high-load caseand the low-load case are just examples showing a high-low relationship,and have no relationship with the load level of the throttle valve 50.

FIG. 6 shows an actual (real) stop position of the rotor relative to anordered stop position of the rotor when the drive load having the levelshown in FIG. 5 is added. The actual stop position is separated largelyfrom an ideal value in the case of high-load because the mountainportion of the torque curve is used, compared with the case of low-load.

In a case where the motor 55 is driven by applying voltage in place ofthe constant current, if the voltage falls, the motor torque also falls.Therefore, the resolution is further lowered in the high-load case. Theair-conditioner apparatus of the present embodiment is for the vehicle.If a battery mounted on the vehicle is lowered, the lowering in theresolution becomes remarkable in the case where the motor is driven byapplying the voltage.

For example, FIG. 7A shows a case where the battery has a voltage of12V, and FIG. 7B shows a case where the battery has a voltage of 8V. InFIG. 7A, the load level is separated far from the mountain portion (peakpart) of the torque curve. However, if the voltage of the battery fallsto 8V, as shown in FIG. 7B, the load level becomes close to the mountainportion of the torque curve, so that the resolution may get worseextremely.

According to the present embodiment, the motor 55 is driven by theconstant current. Therefore, the torque generated by the motor becomesapproximately constant irrespective of the voltage of the power source.For example, even if the voltage of the battery falls from 12V to 8V,the state shown in FIG. 7A can be maintained.

FIGS. 7A and 7B show a schematic torque curve when the motor is drivenin the micro step having four steps, for easy understanding, differentlyfrom FIGS. 4-6. The same thing is applied to FIGS. 8A-9 which are usedfor the subsequent explanation.

According to the embodiment, the step drive control 111 increases theconstant current, as the refrigerant pressure detected by thehigh-pressure side refrigerant pressure sensor 40A becomes large. If therefrigerant pressure is increased on the upstream side of the valve 53in the refrigerant passage 51 a, a refrigerant pressure differencebetween the upstream side and the downstream side of the valve 53 in therefrigerant passage 51 a increases, so that the level of the drive loadis raised.

Therefore, when the motor 55 is driven in the micro step using theconstant current, if the current value is increased based on an increasein the refrigerant pressure upstream of the valve 53 in the refrigerantpassage 51 a, the torque generated by the stepping motor can beincreased correspondingly to the increased drive load. Thus, even if thedrive load becomes large, the motor 55 can be stably driven in the microstep.

In other words, by estimating the load level based on the refrigerantpressure value upstream of the valve 53, and by changing the constantcurrent value based on the estimated load level, the resolution can bemaintained as high.

FIG. 9 illustrates a comparison example relative to the embodiment, inwhich the load level is increased from A level to B level. If theconstant current value is not changed, the torque is not changed fromthe maximum value of X. In this case, a ratio of the load level to themaximum torque X is lowered greatly.

That is, a difference between a value of A/X and a value of B/X becomeslarge, so that the resolution will be lowered greatly.

In contrast, according to the embodiment, the current value of theconstant current drive is increased in accordance with an increase inthe refrigerant pressure upstream of the valve 53 in the refrigerantpassage 51 a. Therefore, as shown in FIGS. 8A and 8B, if the load levelis increased from A level of FIGS. 8A to B level of FIG. 8B, the valueof the constant current is increased, so the torque can be increasedfrom “X1” in FIG. 8A to “X2” in FIG. 8B. Thereby, the ratio of the loadlevel to the maximum torque can be restricted from decreasing. That is,the difference between A/X1 and B/X2 can be made small, so that theresolution can be restricted from having large decreasing, although aslight decreasing may be generated.

The present invention is not limited to the above embodiment.

The number of the micro steps is not limited to sixteen, and can bearbitrarily set.

The step drive control 111 may increase the current value of theconstant current drive based on an increase in a pressure differencebetween the upstream side and the downstream side of the valve 53, inplace of the increase in the refrigerant pressure upstream of the valve53 in the refrigerant passage 51 a. Alternatively, the constant currentvalue may be controlled based on sensor information transmitted fromthree or more sensors.

The motor 55 may be a plural-phase stepping motor other than thetwo-phase stepping motor. For example, The motor 55 may be a five-phasestepping motor.

The motor 55 is not limited to be driven by the constant current. Themotor 55 may be driven by applying a voltage if a predeterminedresolution can be secured.

In the embodiment, the motor 55 is driven in the micro step in the firstflow rate region at the decompression mode, and is driven in the fullstep in the second flow rate region when the mode change is performedbetween the decompression mode and the full-open mode.

In other words, the controller can selectively switch the decompressionmode and the full-open mode. When it is necessary to decompress therefrigerant which circulates in the refrigerant passage 51 a, therefrigerant is decompressed and expanded in the first flow rate regionat the decompression mode. When it is not necessary to decompress therefrigerant, the valve 53 causes the opening degree of the refrigerantpassage 51 a to have the maximum opening so that the refrigerant has themaximum flow rate in the second flow rate region at the full-open mode.

When the valve opening is changed within the first flow rate region, themotor 55 is driven in the micro step. When the operation mode isswitched between the decompression mode and the full-open mode, themotor 55 is driven in the full step. That is, in the second flow rateregion, the flow rate control is performed only at the maximum flowrate.

However, the present invention is not limited to the above control. Forexample, the flow rate control may be performed in the whole of thesecond flow rate region. That is, the motor 55 may be driven in themicro step when the controller controls the valve opening in the firstflow rate region in which the flow rate of refrigerant circulating inthe refrigerant passage 51 a is equal to or lower than a predeterminedvalue. Further, the motor 55 may be driven in the full step when thecontroller controls the valve opening in the second flow rate region inwhich the flow rate of refrigerant circulating in the refrigerantpassage 51 a is higher than the predetermined value.

The refrigerating cycle 3 may be a vapor compression heat pump cycle inwhich the high pressure side pressure is equal to or lower than thecritical pressure, other than the supercritical vapor compression heatpump cycle.

The present invention may be applied to a stationary type refrigeratingcycle other than the refrigerating cycle for the vehicleair-conditioner.

Such changes and modifications are to be understood as being within thescope of the present invention as defined by the appended claims.

1. An expansion valve device arranged in a refrigerating cycle, theexpansion valve device decompressing and expanding refrigerantcirculating in the refrigerating cycle, the expansion valve devicecomprising: a housing defining a refrigerant passage through which therefrigerant circulates; a valve member arranged in the housing so as tochange an opening degree of the refrigerant passage; an electric driverhaving a stepping motor so as to control the opening degree of therefrigerant passage by displacing the valve member in accordance with arotation angle of the stepping motor; and a controller that drives andcontrols the stepping motor, wherein the controller drives the steppingmotor in a micro step when the opening degree is changed within a firstflow rate region where a flow rate of the refrigerant flowing throughthe refrigerant passage is equal to or less than a predetermined value,and the controller drives the stepping motor in a full step when theopening degree is changed within a second flow rate region where theflow rate of the refrigerant flowing through the refrigerant passage islarger than the predetermined value.
 2. The expansion valve deviceaccording to claim 1, wherein the controller selectively switches anoperation mode of the refrigerating cycle between a decompression modeand a full-open mode, in the decompression mode, the refrigerant isdecompressed and expanded within the first flow rate region when it isnecessary to decompress the refrigerant passing through the refrigerantpassage, in the full-open mode, the valve member causes the openingdegree of the refrigerant passage to become the maximum in a manner thatthe flow rate of the refrigerant flowing through the refrigerant passagebecomes the maximum within the second flow rate region when it isunnecessary to decompress the refrigerant passing through therefrigerant passage, and the controller drives the stepping motor in thefull step when the controller switches one of the decompression mode andthe full open mode into the other.
 3. The expansion valve deviceaccording to claim 1, wherein the controller drives the stepping motorin the micro step by supplying a constant current when the openingdegree is changed in the first flow rate region.
 4. The expansion valvedevice according to claim 3, wherein the controller increases theconstant current in accordance with an increase in a pressure differencebetween a pressure of the refrigerant upstream of the valve member and apressure of the refrigerant downstream of the valve member, or thecontroller increases the constant current in accordance with an increasein a pressure of the refrigerant upstream of the valve member.